Instrument for drawing spirals and circles.



W. BRIERLEY.

INSTRUMENT FOR DRAWING SPIRALS AND CIRCLES.

APPLICATION FILED APR. 24.1908.

925,748. Patented June 22,1909.

1n: NcRRls PETERS ca., \IAsNlNcroM, n. c.

WYNFORD BRIERLEY, OF NEW MALDEN, ENGLAND.

INSTRUMENT FOR DRAWING SPIRALS AND CIRCLES.

Specification of Letters Patent.

Patented June 22, 1909.

Application filed April 24, 1908. Serial No. 429,022.

T 0 all whom it may concern:

Be it known that I, Wrnronn BninnLnr, a subject of the King of England,residing at Parkstone, Ooombe Road, New Malden, in the county of Surrey,England, have invented certain new and useful Improvements inInstruments for Drawing Spirals and Circles; and I do hereby declare thefol lowing to be a full, clear, and exact description of the invention,such as will enable others skilled in the art to which it appertains tomake and use the same.

This invention relates to drawing instruments and particularly thatclass known as curve scribers.

The object of the invention is to provide a mechanism of the characternamed wherein are employed two pivoted legs of the common divider typeadapted to be moved in a radial and rotary direction for the purpose ofproducing a spiral but which may be locked against such radial movementat the will of the user and utilized to produce a circle.

A further object of the invention is the production of a mechanism ofthe type set forth and for the purpose named, which will be simple ofconstruction, easy of operation and comparatively inexpensive tomanufacture.

Vith the above and other objects in view the invention consists in thedetails of construction and in the arrangement and combination of partsto be hereinafter more fully described and claimed.

Referring to the drawings :Figure 1 is a front elevation of my improvedmechanism. Fig. 2 is a similar view of a modified form of same, and Fig.3 is a fragment of the mechanism showing the operating stem in section.

In the drawings 6 is a cross head which is formed of the threaded milledboss 7L provided with depending curved arms as shown. A threaded shaft apasses through the boss 7L and operatively engages the threads thereof.The threaded shaft a is bored out longitudinally to receive the spindle0 adapted to work freely in said shaft and held in place by collars (Z.Secured to the outer end of the threaded shaft (4 is a thumb piece 9provided with a small milled head m. A locking nut Z is mounted totravel on the shaft (2 between the boss 72. and thumb piece g. Pivotedto the arms 7 are legs f which are bent inwardly at their lower endwhereby said ends are brought close together. Secured in the lower endsof the legs f are the lengthening bars 70 (shown in dotted lines) whichin turn have secured in their respective ends pin 2' and pencil ormarker j for engagement with the work in operating the mechanism.Secured to the lower end of the spindle 0 through the medium of a commonpivot are the levers or links 6 which have their outer ends pivoted tothe legs f.

The operation of the mechanism illustrated in Figs. 1 and 3 it isbelieved will be obvious. When it is desired to draw a spiral the pin 2'is embedded in the work, the thumb piece 9 held firmly in one hand andthe milled boss 7L rotated to the left with the other hand with theresult that the legs f will be not only rotated but also moved radiallydue to the fact that the shaft a will move downwardly with relation tothe legs f, and thereby force the links 6 to move apart at their outerends and produce a radial movement of the legs f in addition to theirrotary movement such simultaneous radial and rotary movement of saidlegs causing the marker j to trace a spiral. To draw a circle it is onlynecessary to lock the boss it through the medium of the nut Z and rotatethe device by the head m.

In Fig. 2, which shows a modified structure embodying my invention thevarious parts are the same with the exception that the levers c of Fig.l are dispensed with and an angular bar it substituted at the end of thespindle c. This bar is so arranged that its ends are diminished, andsaid diminished portions travel in slots in the legs 0 being held inplace by the enlarged head 9. In this construction the downward movementof the shaft and angular bar n with relation to the legs 0 when the bossh is rotated impart a rotary and radial movement to said legssimultaneously; in other respects the 1 operation is the same as thatdescribed with relation to the structure shown in Fig. 1.

I claim 1. An instrument of the character described comprising a shaft,a member rotathreaded member traveling on said shaft having a pair oflegs pivoted thereto and means whereby the movement of the member 011said shaft imparts a simultaneous radial and rotary movement to thelegs.

3. An instrument of the character described comprising a plurality oflegs, a threaded shaft, a threaded member traveling on said shaft, and apair of links having their outer ends pivoted to the respective legs andtheir inner ends to said threaded shaft, whereby the travel of thethreaded member on the shaft imparts a simultaneous radial and rotarymovement to the legs.

4:. An instrument of the character described comprising a threadedshaft, a threaded member traveling on said shaft having a pair of legspivoted thereto, means whereby the movement of the member on the shaftimparts a simultaneous radial and 20 rotary movement to the legs, andmeans for locking the threaded member against movement on said shaft andradial movement of the legs prevented.

In testimony whereof, I affix my signa- 25

